Does anyone have any info on the difference (if any) in gas mileage by traveling on the highway with the tailgate down vs. up or removed entirely?

 

The old way of thinking, was to leave it down for better mileage. It was proven that to leave it up will produce better mileage. For better mileage, install a soft or hard cover for your bed. Good Luck.

 

the latest studies say, leave the tailgate up, they also say you do get better mpg if you open the windows rather than use the air.....saw it on mythbusters and some truck magazines

 

I saw a recent episode on myth busters where they tested two 05 F150 SC's. The truck with tail gate up went about 30 more miles than the truck with tail gate down before running out of gas.

 

From what Ive seen, tailgate up is better for mpg than tailgate down. With that said, I prefer a tonneau over either setups. Far superior setup. I always boost my mpg, and the truck rolls easier at speed. The way I see/feel it, with the tailgate in place, its like a giant air catcher in place, which slows the truck down. Just my two cents.

 

I agree that a tonneau cover is the best way to improve mpg and handling-to a certain extent. I also seen that mythbusters episode with the model F-150 SC, do you think there would be a diffence between it and oh lets say a regular cab 8 foot box? I would think so.

 

I have seen this study or one like it listed here before but can not find it. It looks like the tonneau cover is best followed by tailgate down then removing the tailgate and last the net. I drive the super duty with the gate down if I am not in town.

Hope this helps

Original link: http://www.enjoythedrive.com/content/?id=10651
another link http://www.dynoproducts.net/fuel&air...ausavesgas.htm

Q: Jerry found us on the web and writes: I read an article from the University Notre Dame concerning wind tunnel testing of pickup trucks. They said that pickups with tailgates up had less drag than trucks with gates down or with "air gates". The reasoning is that the closed gate creates a bubble of stagnant air that dynamic air passes over, therefore lowering overall drag. I suggest you research. If I am correct, please ammend your article on being kind to the environment. Please let me know what you think.
A: SEMA member company Pace-Edwards Co. (2400 Commercial Blvd., Centralia WA, 98531, 800-338-3697, www.pace-edwards.com), makers of pickup bed tonneau covers, recently sent us the results of aerodynamic testing on pickup trucks performed at the Western New England College School of Engineering. The test results were quite illuminating, so we thought we'd share them with you.

At Western New England College, Todd Ortolani and Vanwijak Ewosakul, under the leadership of Dr. Alan Karplus, an in-depth study on the effect of airflow once it passes the truck's cab was performed. The flow separates behind the cab and enters the truck bed resulting in a drag coefficient (Cd) of Cd = .432 if the bed is not covered. When a square truck cap is added, the drag coefficient increases to Cd=.480, or an 11.11% increase in drag.

When a tonneau cover is used, the drag coefficient decreases to Cd=.381, or an 11.81% decrease in drag. Additional comparisons were made in the study by changing the tailgate. Replacing the tailgate with a cargo net resulted in Cd=.461, a 6.71% increase in drag compared to removing the tailgate which resulted in a Cd=.447, a 3.47% increase in drag. Also, lowering the tailgate resulted in Cd=.414, a 4.17% decrease in drag. The results of this study concluded that the best method of decreasing the drag coefficient, thus increasing fuel economy, is to install a tonneau cover over the truck bed.

Please note that the results from this test do not agree with the results you have cited. It's not a great mental stretch to understand that different makes and models of trucks are likely to produce different results, even in the controlled environment of the wind tunnel. We would fully expect to see, for example, that a truck with a standard bed and the same truck with a step-side bed, would have different results. Additionally, different brands of pickup trucks will have different configurations in the tailgate area.

Some trucks have a slight amount of "wrap around" in the rear corners of the bed where the side wall of the bed actually forms a small upright section as it turns the corner to meet the tailgate. In other trucks, the tailgate spans the entire rear section of the bed, and when opened, it leaves no upright section at the rear of the bed. Would these two designs post different drag coefficients?

Furthermore, would it also not be possible that the length of the bed plays a part in all of this? Certainly a truck with an eight-foot bed is going to post different results than a truck with a six-foot bed. That being the case, what about the new crop of four-door pickups that have beds under five feet in length?

As far as air gates are concerned, the Western New England College study found that the drag coefficient increased with its use by Cd= 0.029. This would seem to bear out the results of the test you are quoting. But this does not take into consideration the weight advantage the air gate enjoys over a standard tailgate. A standard tailgate weighs 40 lbs. or more depending on the truck. An air gate weighs about 8 lbs. with its attaching hardware. While they create more drag according to these tests than a standard tailgate, a 32 lb. weight advantage has to count for something when measuring fuel economy, which is really what we were talking about in the first place.

Weight is a very serious consideration when talking about fuel economy. If we could build two identical pickup trucks, one with an all steel bed, and the other with a lighter fiberglass bed assembly, even though they have the same coefficient of drag, wouldn't the lighter truck get better mileage?

This then begs the question, how much would we need to improve the coefficient of drag of the heavier truck to match the advantage the lighter weight truck enjoys? Pace-Edwards has shown that the use of their tonneau covers lower the coefficient of drag on their test truck by Cd=0.051 or 11.81% over an uncovered bed with the tailgate up. Additionally, they have testimonials from users of their products that they have noted improvements in fuel economy since installing their tonneau covers on various makes and models of trucks.

The point of all these cerebral calisthenics is that test results like those we have quoted, and you have cited, can vary widely. Do the companies that say their products improve aerodynamics have test results to back up their claims? Some apparently do, while we can not speak for others.

 

Regardless of the above discussion, I think leaving the tailgate down makes it far more prone to damage, i.e., no bumber protection. Also, I can't imagine that the bouncing of the tailgate when left down for extended periods of time will be good for the hinges, welds, etc. They were designed to be in the up position normally.

 

Trucks are tested in wind tunnels now. They are tested with the tailgate up. Guess which way they will be more efficient?

Older trucks that were not wind tunnel tested are anybodies guess. However simple variation of driving habits are likely to be high enough to obscure any difference. I'm going to leave mine up. Makes it easier to show the big FORD on the tailgate to rice burners and chevys that can't keep speed uphill.

 

i dont go around with my gate down all the time. but the times that i have i havent, noticed no extra mileage loss. the way i figured this is, unless i'm going over the road i only get 15 gals of gas a week. i figure my mpgs on 15. thats 225 total. i've never had to get gas before the 225 mark. i've have gone alittle longer. i know this is a butchers method rather than a scioenceist's. my point is if some reason or other you have to have the gate down i would'nt worry about gas running out the tailpipe. my self i think a truck going down the road with its gate down or removed looks tacky, but then thats me. i think it would take more than a wind tunnel to come up with a real true conclusion. you could try it and see how you come out. with your driving habits it might help you....